I've been wondering how close my 392's with 17" rims compared to the 410's with 20" rims (compared in gear ratios). At 70 mph I'm reading an easy 2000 rpms, what are you RT guys reading at the same speed? I do know that the tires on the 20's are at least 2" taller than the ones on mine so that would bring our gear ratios a little closer in comparison. I'm well aware that this won't be accurate, but I'm hoping your answers will be close, tks .

 

Try the last calculator on the page. Use .67 for the transmission final gear ratio, that is our fifth gear.

It is titled "Transmission Final Gear Ratio Manual Entry".
http://www.csgnetwork.com/multirpmcalc.html

 

Not sure at 70mph but I know at 80mph I'm turning about 2,200-2,300rpms

 

With 3.92 gears and my tire height being 31" I get 1993 rpms at 70 mph which is about right, close enough to my visual 2000 rpms at 70. I calculated it using 410 gears with what I think 20" tires has 33" height, and I get 1958 at 70 mph. This tells me that my gear ratio to tire height is equal to the RTs with 4.10 with 33" tires. Now, just how tall are the tires on the RT, are they 33", can anyone tell me? If so, I'm at least equal or better yet, lower than the RTs, awesome!